Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 270730
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 AM EDT Tue Jun 27 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 330 AM EDT Tue Jun 27 2017

High pressure will provide plenty of sunshine today although
temperatures will remain below normal. It will not be as windy as
yesterday.

On Wednesday and Wednesday night a warm front will push in from
the southwest, resulting in showers and thunderstorms. The best
coverage of storms will be north and west of Grand Rapids.

The main thunderstorm risk on Thursday is expected to be south of
Michigan, but that risk will expand north again on Friday and
Friday night.

&&

.SHORT TERM...(Today through Thursday)
Issued at 330 AM EDT Tue Jun 27 2017

Main focus is on convective potential Wednesday through Thursday.

Models have been consistent in showing a 50 to 60 knot swly low
level jet developing on Wednesday over Wisconsin as a shortwave
tracks across the Dakotas and Minnesota. This setup is expected to
fuel widespread showers and storms over central and northern Wisconsin,
which should work into western and northern lower Michigan in the
afternoon and evening.

Current model QPF solutions indicate the heaviest rain, on the
nose of the low level jet, should pass to our north. However the
nnw-sse orientation of the thickness pattern may cause the WI
storms to curve/propagate more southeastward, at least initially,
which could lead to a heavy rain threat for a time Wednesday night
north of a line from roughly Holland to Alma. The main axis of
heavy rain lifts toward northern Lake Huron later Wed night as
the shortwave moves toward Lake Superior.

It would appear that Thursday may end up being relatively quiet
since the low level jet peels away and we end up with a divergent
low level westerly flow over the area. This pattern usually keeps
most of the area dry, although some diurnal storms could pop
along and south of I-94 where sfc convergence will exist along the
sfc cold front which slips south through our area in the morning.

In the near term, Today looks rather quiet as the upper
trough begins to slowly lift out and sfc ridging impacts the
area. Can`t rule out an isolated shower or two in far eastern
sections.


.LONG TERM...(Thursday night through Monday)
Issued at 330 AM EDT Tue Jun 27 2017

Active wx is anticipated during the early portion of the long range
fcst period with potential for several rounds of convection. There
is potential for showers and storms Thursday night with a lingering
frontal boundary over the lower Great Lakes region.

Initially Thursday evening the better chance for convection should
be just south of our area across northern IL/IN/OH, but the boundary
will likely move north Thursday night. An increasing nocturnal llj
will also focus some convective development.

A better chance for more widespread convection will come Friday as a
low pressure system and cold front move through. Some strong to
severe storms are possible given lift from the approaching front in
conjunction with ample low level moisture and potential for moderate
instability to develop. Deep layer shear values of 35 to 45 kts are
also favorable for some strong to potentially severe storms.

Larger medium range guidance discrepancies arise for the weekend
into early next week leading to lower confidence in that portion of
the fcst. Initially a somewhat cooler and drier airmass will move in
behind the cold front for the weekend. However there are some
signals in longer range guidance that the wx pattern could turn more
active again early next week as another system potentially moves in
from the west late Monday or Tuesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1143 PM EDT Mon Jun 26 2017

Vfr conditions will continue at all the terminals through Tuesday
evening. Sct-bkn fair wx cu will develop Tuesday and isolated
light rain showers may affect our eastern terminals (KLAN and
KJXN) Tuesday afternoon. West winds will increase to around 10-15
kts Tuesday but winds will not be as strong as they have been the
past several days. Skies will clear at all the terminals Tuesday
evening.


&&

.MARINE...
Issued at 330 AM EDT Tue Jun 27 2017

Still some 4 foot waves from South Haven south early this morning,
but the trend should be for subsiding waves toward as high
pressure impacts the region. Small Craft Advisories and Beach
Hazard Statements will likely be needed again Wednesday as winds
increase considerably from the south.

&&

.HYDROLOGY...
Issued at 1119 AM EDT Mon Jun 26 2017

River levels are trying to return to normal across the region...with
the Chippewa River at Mt. Pleasant and Pine River at Alma above flood
stage. Scattered showers and thunderstorms...which will develop as
an upper low moves over the state this afternoon...are not expected
to produce the areal coverage or intensity of precipitation needed
to slow the falling of the stages. Therefore...expect river levels
to continue to fall steadily over the next 24 hours.

Another round of potentially heavy rainfall will occur later
Wednesday into Wednesday night. Deep moisture returns to the
region...and bands of heavy rainfall may occur across central
portions of Lower Michigan. Rivers in Isabella and Gratiot
counties are especially vulnerable to excessive rainfall...and
significant rises would likely develop on the Pine and Chippewa
rivers should the heavy rainfall occur in these basins.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 5 AM EDT early this morning for
     MIZ037-043-050-056-064-071.

LM...Small Craft Advisory until 5 AM EDT early this morning for
     LMZ844>849.

&&

$$

SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...Laurens
AVIATION...Laurens
HYDROLOGY...MWS
MARINE...Meade


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